---
name: "cas"
section: "4"
platform: "freebsd"
package: "base"
version: "16.0-CURRENT-20261027-61c70dc16a79"
release: "FreeBSD 16.0-CURRENT (2026-10-27)"
platforms: ["freebsd", "openbsd"]
url: "https://new.carta.tech/cas/4"
---

# cas(4)

Sun Cassini/Cassini+ and National Semiconductor DP83065 Saturn Gigabit Ethernet driver

## NAME

**cas** – Sun Cassini/Cassini+ and National Semiconductor DP83065 Saturn Gigabit Ethernet driver

## SYNOPSIS

To compile this driver into the kernel, place the following lines in your kernel configuration file:

**device miibus** **device cas**

Alternatively, to load the driver as a module at boot time, place the following line in [loader.conf(5)](/loader.conf/5.md):

```
if_cas_load="YES"
```

## DESCRIPTION

The **cas** driver provides support for the Sun Cassini/Cassini+ and National Semiconductor DP83065 Saturn Gigabit Ethernet controllers.

All controllers supported by the **cas** driver have TCP/UDP checksum offload capability for both receive and transmit, support for the reception and transmission of extended frames for [vlan(4)](/vlan/4.md) and an interrupt coalescing/moderation mechanism as well as a 512-bit multicast hash filter.

The **cas** driver also supports Jumbo Frames (up to 9022 bytes), which can be configured via the interface MTU setting. Selecting an MTU larger than 1500 bytes with the [ifconfig(8)](/ifconfig/8.md) utility configures the adapter to receive and transmit Jumbo Frames.

## HARDWARE

The chips supported by the **cas** driver are:

- National Semiconductor DP83065 Saturn Gigabit Ethernet

- Sun Cassini Gigabit Ethernet

- Sun Cassini+ Gigabit Ethernet

The following add-on cards are known to work with the **cas** driver at this time:

- Sun GigaSwift Ethernet 1.0 MMF (Cassini Kuheen) (part no. 501-5524)

- Sun GigaSwift Ethernet 1.0 UTP (Cassini) (part no. 501-5902)

- Sun GigaSwift Ethernet UTP (GCS) (part no. 501-6719)

- Sun Quad GigaSwift Ethernet UTP (QGE) (part no. 501-6522)

- Sun Quad GigaSwift Ethernet PCI-X (QGE-X) (part no. 501-6738)

## SEE ALSO

[altq(4)](/altq/4.md), [miibus(4)](/miibus/4.md), [netintro(4)](/netintro/4.md), [vlan(4)](/vlan/4.md), [ifconfig(8)](/ifconfig/8.md)

## HISTORY

The **cas** device driver appeared in FreeBSD 8.0 and FreeBSD 7.3. It is named after the **cas** driver which first appeared in OpenBSD 4.1 and supports the same set of controllers but is otherwise unrelated.

## AUTHORS

The **cas** driver was written by Marius Strobl ⟨*marius@FreeBSD.org*⟩ based on the [gem(4)](/gem/4.md) driver.